Wastewater effluent from certain industrial processing contains minor quantities of oil. Such operations include the coiled metal and food processing industries. The oil discharged into the effluent wastewater has generally been "washed" from the primary processing operation by soaps and surfactants. Consequently, it is primarily in the form of emulsified, randomly dispersed, minute negatively charged particles and is generally not in the form of an oily layer on the surface of the water.
Traditional methods used to remove the oil waste include the use of aluminum containing compounds, such as aluminum sulfate. The soluble Al.sup.+3 ion from these compounds reacts with the aqueous medium to form a precipitate of aluminum hydroxide. This precipitate contains the oil contaminant, the combination of which is referred to as sludge.
Additionally, in the processing of food products, it is frequently desired to reuse the waste oils and fats as additives to the food given to livestock. However, if aluminum products are used to remove the oils and fats, it is possible that the livestock may become ill. This either limits the use of treatments with aluminum compounds or negates the use of recycled oils and fats.
Where the emulsion is especially troublesome, such as in the steel coil and container industry, acid, e.g., H.sub.2 SO.sub.4, may be required as an emulsion breaker. Disadvantages of adding H.sub.2 SO.sub.4 to the aqueous system include the increased safety risk due to operator handling, the addition of lime to neutralize the system pH after the addition of acid and the formation of a calcium sulfate precipitate which adds bulk to the sludge solids.